1. Field of the Invention
The present invention relates to the field of display technology, and more particular to an OLED packaging method and an OLED package structure.
2. The Related Arts
Organic light-emitting display (OLED) possesses various advantages, such as being self-luminous, low drive voltage, high luminous efficiency, short response time, high clarity and contrast, almost 180° view angle, wide range of operation temperature, and easy realization of flexible displaying and large-area full-color displaying, and is considered the most promising display device in the industry.
Based on the way of driving, OLEDs can be classified in two categories, passive matrix OLED (PMOLED) and active matrix OLED (AMOLED), namely two categories of direct addressing and TFT array addressing, among which the AMOLED comprises pixels that are arranged in an array and belongs to an active display type, having high light emission performance and being commonly used in high definition large-sized display devices.
An OLED device is generally made up of a substrate, an anode arranged on the substrate, a hole injection layer arranged on and anode, a hole transport layer arranged on the hole injection layer, an emissive layer arranged on the hole transport layer, an electron transport layer arranged on the emissive layer, an electron injection layer arranged on the electron transport layer, and a cathode arranged on the electron injection layer. The principle of light emission of the OLED device is that when a semiconductor material and an organic light emission material are driven by an electric field, carrier currents are injected and re-combine to cause emission of light. Specifically, the OLED device often uses an indium tin oxide (ITO) electrode and a metal electrode to respectively serve as anode and cathode of the device and electrons and holes, when driven by a predetermined electrical voltage, are respectively injected into the electron transport layer and the hole transport layer from the cathode and the anode such that the electrons and the holes respectively migrate through the electron transport layer and the hole transport layer to get into the emissive layer and meet in the emissive layer to form excitons to excite light emissive molecules to emit light, the later undergoing radiation relaxation to give off visible light.
The OLED device is very sensitive to moisture and once exposed in moisture, the cathode might get oxidized and the organic layers (the hole injection layer, the hot transport layer, the emissive layer, the electron transport layer, and the electron injection layer) may be degraded so as to reduce the brightness and service life of the OLED device. Thus, a packaging material of an OLED device must exhibit powerful capabilities of resisting external moisture and oxygen in order to improve the brightness and service life of the OLED device.
Diamond-like carbon (DLC) is a material that possesses relatively good characteristics of blocking moisture and oxygen and has prosperous future of application in the field of OLED packaging. As early as the year 2005, Abbas has reported, in an article published in Thin Solid Films 482 (2005) 201-206, systematic researches in respect of water vapor transmission rate (WVTR), refractive index, and light transmission rate of diamond-like carbon and the results of the researches reveal the water vapor transmission rate of the diamond-like carbon is reduced with an increase of the thickness thereof, and when the thickness of the diamond-like carbon reaches around 70 nm, the water vapor transmission rate no longer shows significant reduction. On the other hand, introduction of a minor amount of element silicon (Si) in the diamond-like carbon may increase the capability of blocking moisture and oxygen, but reduces the density, transmission rate, and refractive index. Thus, effectively dissolving confliction between the capability of the diamond-like carbon for blocking external moisture and oxygen and the density, transmission rate, and refractive index thereof is directly linked to actual applications of diamond-like carbon.